"We don't have any documented dinosaur bones and teeth from that period in North America, except for some very scrappy material from Mexico," said Brent Breithaupt, curator and director of the University of Wyoming's Geological Museum in Laramie, Wyo. That makes it very hard to connect the tracks to a particular dinosaur. And of course, "We unfortunately can't go out and see walking dinosaurs today. Or can we?"
After scouring the dinosaur fossil record in other parts of the world and deciding that a human-sized, meat-eating dinosaur (theropod) fit the bill for the tracks at Red Gulch, Breithaupt and his colleagues and students did something unusual. Instead of speculating about what the dinosaurs were doing, they went hunting for a modern analog animal they could study to help decipher the tracks.
Large flightless birds are the most logical choice and are, along with all birds today, thought to be descended from dinosaurs. But not all of those alive today are good choices or easy to work with. Ostriches are two-toed and have an attitude problem, so that ruled them out, says Breithaupt. Rheas have three toes, but are "like working with a bunch of kindergarteners on too much sugar," he said.
That left emus, which are perfect: three toes, the right size, and relatively easy to work with. What's more, there is an emu ranch handily located in nearby Colorado at which Breithaupt and his team could reconnoiter and learn emu "dance steps."
"So we went from walking from dinosaurs to walking with emus," he sa
Source:Geological Society of America